The present invention generally relates to methods and systems for inputting coordinates using a digitizer, and more particularly to a method and a system for inputting coordinates from a digitizer to a display device having a display area larger than a corresponding area of the digitizer.
It is known to make the area of a pointing region of the digitizer correspond to the display area of the display device and point an arbitrary point on the digitizer pointing region so as to display on the display area a cursor which corresponds to the arbitrary point. The number of points which can be pointed on the digitizer pointing region is normally set greater than or equal to the number of points which can be displayed on the display device. When the number of points which can be pointed on the digitizer pointing region is set greater than the number of points which can be displayed on the display device, this means that the resolution of the digitizer is greater that the resolution of the display device.
When the size of the digitizer is reduced compared to that of the display device, the resolution of the digitizer must be increased if the number of points which can be pointed is the same for the digitizer and the display device. However, because the resolution of the digitizer cannot be increased infinitely, there is a limit to reducing the size of the digitizer.
An example of a conventional method of pointing the display area from the digitizer will be described in conjunction with FIG. 1. When a pen 12 points a point P.sub.1 on a pointing region of a digitizer 10, a cursor is displayed at a corresponding point P.sub.2 on a display 14 of a display device 15. For example, the cursor may take the form of a line, a square, a dot or the like. The dots in the pointing region of the digitizer 10 correspond one-to-one to the dots on the display 14, and the number of dots in the pointing region of the digitizer 10 is greater than or equal to the number of dots on the display 14 so that all dots on the display 14 can be pointed from the digitizer 10.
There are various kinds of digitizers. In the case of the digitizer having a large number of lines in the X and Y directions, each dot is an intersection point of one line in the X direction and one line in the Y direction. In addition, a cathode ray tube (CRT) provided with an image memory is often used for the display 14 of the display device 15, and the dots on the display 14 correspond to pixels of the image memory. In other words, the number of dots arranged in the horizontal scanning direction is equal to the number of pixels in one line, and the number of dots arranged in the vertical direction is equal to the number of horizontal scanning lines of one picture. For example, there are 640 (horizontal direction).times.400 (vertical direction) dots on the display 14 of the display device 15, while there are 1280 (horizontal direction).times.800 (vertical direction) dots in the pointing region of the digitizer 10. When the number of dots in the pointing region of the digitizer 10 is greater than (four times) the number of dots on the display 14 of the display device 15 as is the case of this example, four dots in the pointing region of the digitizer 10 correspond to one dot on the display 14, and the same one dot will be displayed on the display 14 regardless of which one of the above four dots in the pointing region is pointed.
According to the conventional method which makes the digitizer pointing region correspond to the display area so that the dots correspond one-to-one therebetween, the dot density of the digitizer pointing region becomes large compared to that of the display device as the size of the digitizer is reduced. If the digitizer is of the type which uses a large number of lines in the X and Y directions, it becomes necessary to arrange the lines in the X and Y directions with a high density. However, there are problems in that it is technically difficult to make a digitizer having the lines arranged with such a high density and it becomes difficult to point the dot using the pen because the intersection points (dots) of the lines in the X and Y directions are arranged extremely close to each other because of the high density arrangement.